Answer: the steel wool in the 3.0 M HCl reacts fastest. 
Explanation:
 
        
             
        
        
        
Answer:
A) Hummingbirds drinking nectar from a plant.
Step-by-step explanation:
Here are some examples of natural selection: In a habitat there are red bugs and green bugs. The birds prefer the taste of the red bugs, so soon there are many green bugs and few red bugs. The green bugs reproduce and make more green bugs and eventually there are no more red bugs.
 
        
                    
             
        
        
        
Answer:
A string is placed under a solution and a crystal grows on the string because the solution is supersaturated. 
Therefore, the correct answer to the question is option B.
Explanation:
A saturated solution is defined as a solution in which there is no more space for the solute to be added. All the words in the solution is been filled with the solute which is been added before and mixed well to fill up all the pores. Supersaturated solution is defined as a solution which has a greater number of solute than it was being capable of holding. 
As it is clear from the name supersaturated which means more than saturation. And when string is placed under this solution there are some crystal which grows on the strings because of the solute saturation which is being attached to the string.
 
        
             
        
        
        
Answer:
option B
Explanation:
The correct answer is option B
Cells are the basic structural and functional unit of life and possess genes. These genes evolve to carry out new biological functions in the body.  
Cells undergo division and growth whether it be unicellular organisms or multi cellular organisms.  
All cells possess the property of compartmentalization and metabolism henceforth taking up nutritive material from the environment. 
These nutrients are further transformed into the cell compartments and the waste produced as a result is expelled out thus forming on open system.